The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. Unless otherwise identified as prior art, the subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.
Internal combustion engine and electric motor powered vegetation trimmers are commonly used to cut and trim grass, weeds, brush and other vegetation. The typical motorized trimmer may include an elongated handle to which is connected an internal combustion or electric motor that rotatably drives a trimmer head located at a distal end of the handle. This machine is “handheld”.
The trimmer head (e.g., a rotary cutting head attachment to a driveshaft of a trimmer), in turn, carries radially outwardly projecting cutting implements, which cut the vegetation as the trimmer head rotates. In addition to “handheld” vegetation cutting machines there are also wheeled type vegetation trimmers, which are gas powered, and utilize an engine that generates much greater horsepower than any “handheld” type machine, the trimmer and cutting machines are designed to cut very dense (e.g., thick) vegetation and brush. These trimmer machines use some types of cutting heads that are used with the “handheld” trimmer machines.
The trimmer head may include one or more flexible monofilament line or rigid cutting implements. Rigid cutting implements (a cutting means) typically assumes the form of blades fabricated from plastic and or metal and often have corrugations or scalloping about their peripheral cutting edges. They are a unitary one-piece cutting blade molded from a durable high strength plastic/metal material with plurality of cutting arms extending outward from the hub. The pivoting type rigid blades are attached to circular pins mounted vertically on the peripheral portion of trimmer head body, and the body is attached directly to the trimmer machine's driveshaft. The pivoting blades yield when they contact hard objects, thereby prolonging the service life of these blades. Other fixed rigid type blades mount directly to the trimmer driveshaft. Both of these above mentioned vegetation cutting blades are normally used to cut very dense and thick grasses, and weeds to include brush. Other forms of rigid type of cutting blades are used on handheld and wheeled type trimmer machines alike. A usage of rigid cutting blades is for cutting, weeds, small bushes, corn stalks, brush, saplings having a small diameter, 3″ thick, for example. Rigid blades may be made from a metal disc (e.g., a circular plate) that is attached to the driveshaft of the trimmer machine and mounted around the periphery of the metal disc is a series of chainsaw cutting teeth as used on a “Chainsaw.” All of the above mentioned types of blades may cause considerable injury to the trimmer operator or other persons during operation of the trimmer, should the operator or other persons be accidentally struck by one of these types of blades, if they are made of metal or hard, rigid, sharp plastic material.
Generally, weeds growing on footpaths between rice fields etc. have to be cut several times a year because they tend to be nested by pests. The weed cutting is usually very laborious, and thus various automatic weed cutters have heretofore been proposed and put to practical use, among which shoulder-hung weed cutters are very popular because of their small size and handling ease. In most of the shoulder-hung weed cutters, a driving-force transmission shaft or driveshaft, which is passed through a pipe-shaped handling rod, is rotated via an engine provided at one end of the handling rod so as to rotate a cutter blade provided at the other end of the handling rod.
In most cases, a human operator hangs the weed cutter on his or her shoulder using a hanging belt, and cuts weeds with the rotating cutter blade by gripping a U-shaped handle provided on an intermediate position of the handling rod to swing the handling rod in front-and-rear and left-and-right directions.
Both in light duty, medium and heavy duty gas and electric powered trimmers, the cutting implements may be fabricated as a continuous strand flexible monofilament plastic line wrapped about a spool contained within the trimmer head. In such devices, the plastic line is typically selectively dispensed by the centrifugal force generated by rotation of the trimmer head.
A disadvantage common to these sorts of devices is that the line quite frequently becomes jammed when a user attempts to dispense fresh line from the spool and the line prematurely breaks off at the eyelet because the diameter of the line is small and has little tensile strength when making contact with hard objects and heavy vegetation. When this occurs, the user generally must stop the trimming operation, disassemble the trimmer head, fix the jam and or extend line through the eyelets and reassemble the trimmer head before resuming trimming. Such repeated disruption is very frustrating and time-consuming by the end user. It should be noted that spool heads of automatic and semi-automatic type, include a line cutting blade on the debris shield. When the head is bumped on the ground and dispenses the line, more line is generally extended from the storage spool than needed, and the blade on the shield cuts off the extra line.
Another species of vegetation trimmer cutting apparatuses are automatic spool trimmer heads. This type of trimmer cutting head is called “automatic trimmer head.” The automatic trimmer heads require no tapping on the ground and automatic trimmer heads always feed out a set length of trimmer line.
Another species of vegetation trimmer, where trimmer line is selectively dispensed from a spool by an operator, is fully manual in operation. Devices of this sort include at least one or more, typically spring-biased, indexing pins or buttons that are connected to one or more internal trimmer line carrying spools. In order to dispense trimmer line, an operator displaces the indexing pins or buttons from a seating engagement with one or more holes provided in the trimmer head housing.
Once the indexing pin(s) or button(s) are separated from the housing, the user either turns the internal spool(s) or pulls on the trimmer line itself from the spool in order to pay out the line from the trimmer head. When the desired length(s) of trimmer line have been dispensed, the operator reseats the indexing pin(s) or button(s) into their associated indexing opening(s) in the trimmer head housing.
Another species of spool trimmer heads has surfaced, which is very distinctly and substantially different from prior art examples of spool trimmer heads described and reference above. Typically, reloading fresh line into a spool trimmer head is a difficult and time consuming process. All the prior art reference spool trimmer heads reference above, require some form of disassembly of the trimmer head components prior to loading or reloading new trimmer line onto the spool.
Spool type trimmer heads often have some form of anchoring means to secure one or more fixed lengths of line to the hub of the spool prior to wrapping the lengths of line onto and around the spool hub.
Another species of vegetation trimmer heads employs finite or fixed cut lengths of monofilament (nylon) plastic line or string that can be quickly and easily replaced as they become broken or worn, without need to resort to disassembly and reassembly of the trimmer head.
In this category of trimmer heads the finite length(s) of trimmer line are securely held in a fixed position within the trimmer head body by different methods (i.e., weaving means, different types and forms of clamping means with and without mechanical bias, special injection molded flails that have a special end portion of the cutting flail that holds the finite length of cutting line securely in the body of the trimmer head during cutting operations, etc.). All of the these fixed length types of line vegetation trimmer cutting heads provide the end user a more user friendly trimmer head product vs. the standard spool “bump and feed” product.
Fixed length trimmer heads have the benefit of making the replacement of worn flexible cutting line and the loading of new flexible cutting line much easier. These types of trimmer heads allow the end user the opportunity the ability to use a broad range of flexible lines having many diameters (e.g., diameters including 0.065″ to 0.155″). These trimmer heads typically weigh less and are less expensive to manufacture. Since fixed length type vegetation cutting heads can receive and hold a wide range of differently sized trimmer lines, a customer can select the size of line that works best with the size and power of the machine available. Too large of a flexible cutting line diameter and too long of a length extending from the exit ports of the head will deplete the rotational speed and power because of air drag caused by the size of the cutting line. There is a wide variety of electric and gas powered trimmer machines manufactured and they also have a wide range of power ratings per machine. It is important to select and use the right cutting attachment with different machines so that they will work efficiently and safely during operation.